<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>彩虹</title>
    <style>
      .rainbow {
        width: 600px;
        height: 300px;
        background-image: radial-gradient(
          circle farthest-side at bottom center,
          white 40%,
          rgb(19, 3, 245) 50%,
          rgb(19, 3, 245) 55%,
          rgb(4, 252, 25) 60%,
          rgb(4, 252, 25) 65%,
          rgb(240, 240, 4) 70%,
          rgb(240, 240, 4) 75%,
          rgb(245, 160, 4) 80%,
          rgb(245, 160, 4) 85%,
          rgb(245, 4, 4) 90%,
          rgb(245, 4, 4) 95%,
          white 95%
        );
      }
    </style>
  </head>
  <body>
    <div class="rainbow"></div>
  </body>
</html>
